Azeotrope-like composition of 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf) and hydrogen fluoride (HF)

ABSTRACT

Provided are azeotropic and azeotrope-like compositions of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) and hydrogen fluoride (HF). Such azeotropic and azeotrope-like compositions are useful as intermediates in the production of 2,3,3,3-tetrafluoropropene (HFO-1234yf).

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional patentapplication Ser. No. 61/034,184, filed Mar. 6, 2008, which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to azeotropic and azeotrope-likecompositions of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) andhydrogen fluoride (HF). More particularly the invention pertains to suchazeotropic and azeotrope-like compositions which are useful asintermediates in the production of 2,3,3,3-tetrafluoropropene(HFO-1234yf).

2. Description of the Prior Art

Traditionally, chlorofluorocarbons (CFCs) like trichlorofluoromethaneand dichlorodifluoromethane have been used as refrigerants, blowingagents and diluents for gaseous sterilization. In recent years there hasbeen universal concern that completely halogenated chlorofluorocarbonsmight be detrimental to the Earth's ozone layer. Therefore,stratospherically safer alternatives to these materials are desirable.Consequently, there is a worldwide effort to use fluorine-substitutedhydrocarbons which contain fewer or no chlorine substituents. In thisregard, 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf), having low ozonedepletion potential, is being considered as a replacement forchlorofluorocarbons such as dichlorodifluoromethane in refrigerationsystems and trichlorofluoromethane as a blowing agent. The production ofHFC's, i.e. compounds containing only carbon, hydrogen and fluorine hasbeen the subject of interest to provide environmentally desirableproducts for use as solvents, blowing agents, refrigerants, cleaningagents, aerosol propellants, heat transfer media, dielectrics, fireextinguishing compositions and power cycle working fluids. It is knownin the art to produce fluorocarbons such as HFC's by reacting hydrogenfluoride with various hydrochlorocarbon compounds. Such HFC's are notonly considered to be much more environmentally advantageous thanhydrochlorofluorocarbons (HCFC's) or chlorofluorocarbons (CFC's) becausethey are not non-ozone depleting, but also they are non-flammable, andnon-toxic as compared to the chlorine containing compounds.

HCFO-1233xf is an intermediate in the production of2,3,3,3-tetrafluoropropene (HFO-1234yf) which is well known in the artas described in U.S. Applications 20070007488 and 20070197842, thespecifications of which are incorporated herein by reference. HFO-1234yfhas been disclosed to be an effective refrigerant, heat transfer medium,propellant, foaming agent, blowing agent, gaseous dielectric, sterilantcarrier, polymerization medium, particulate removal fluid, carrierfluid, buffing abrasive agent, displacement drying agent and power cycleworking fluid.

It has now been found that an important intermediate in the productionof substantially pure HFO-1234yf, is an azeotropic or azeotrope-likecomposition of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) andhydrogen fluoride. This intermediate, once formed, may thereafter beseparated into its component parts by known extraction techniques. Theazeotropic and azeotrope-like compositions find use not only asintermediates in the production of HFO-1234yf, but they are additionallyuseful as nonaqueous etchant mixtures for etching semiconductors in theelectronics industry, as well as compositions for removing surfaceoxidation from metals. In addition, the formation of an azeotropic orazeotrope-like composition of HCFO-1233xf and hydrogen fluoride isuseful in separating a mixture of HCFO-1233xf and an impurity such as ahalocarbon, for example, 1,1,1,2,3-pentachloropropane;1,1,2,3-tetrachloropropene; 2,3,3,3-tetrafluoropropene;2,3-dichloro-3,3-difluoropropene; 1,1,1,2,2-pentafluoropropane; or1,2-dichloro-3,3,3-trifluoropropene. When it is desired to separate amixture of HCFO-1233xf and an impurity, HF is added to form anazeotropic mixture of HCFO-1233xf and hydrogen fluoride, and then theimpurity is removed from the azeotropic mixture, such as by distillationor other known means. This binary azeotrope or azeotrope-likecomposition is then available for separation into its component parts.

SUMMARY OF THE INVENTION

The invention provides an azeotropic or azeotrope-like compositionconsisting essentially of hydrogen fluoride and2-chloro-3,3,3-trifluoropropene.

The invention further provides a method of forming an azeotropic orazeotrope-like composition which comprises forming a blend consistingessentially of from about 6.2 mole percent to about 90.7 mole percenthydrogen fluoride and from about 9.3 mole percent to about 93.8 molepercent 2-chloro-3,3,3-trifluoropropene to thereby form an azeotropic orazeotrope-like composition having a boiling point of from about 0° C. toabout 61° C. at a pressure of from about 15 psia to about 107 psia.

The invention also provides a method for removing2-chloro-3,3,3-trifluoropropene from a mixture containing2-chloro-3,3,3-trifluoropropene and at least one impurity, whichcomprises adding hydrogen fluoride to the mixture in an amountsufficient to form an azeotropic or azeotrope-like composition of the2-chloro-3,3,3-trifluoropropene and the hydrogen fluoride, andthereafter separating the azeotropic composition from the impurity.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a plot of the vapor pressures of the mixtures formed inExample 2 as measured at 0° C., 25° C. and 61° C.

DETAILED DESCRIPTION OF THE INVENTION

In a method of preparing an HCFO-1233xf precursor, reagents arefluorinated with hydrogen fluoride. This may be done, for example, bythe gas phase catalytic fluorination of CCl₂=CClCH₂Cl with HF to yieldHCFO-1233xf. Such methods are disclosed in U.S. Application 20070197842,the specification of which is incorporated herein by reference. Thereaction products of such precursors include HCFO-1233xf, unreacted HFand other by-products. Upon removal of the by-products, a binaryazeotrope or azeotrope-like composition of HCFO-1233xf and HF is formed.This binary azeotrope or azeotrope-like composition is then availablefor separation into its component parts. The azeotropic orazeotrope-like compositions of the HCFO-1233xf and HF are also useful asrecycle to the fluorination reactor. Thus, for example, in a process forproducing HCFO-1233xf, one can recover a portion of the HCFO-1233xf asan azeotropic or azeotrope-like composition of HCFO-1233xf and HF andthen recycle the composition to the reactor.

HCFO-1233xf forms azeotropic and azeotrope-like mixtures with HF. Thethermodynamic state of a fluid is defined by its pressure, temperature,liquid composition and vapor composition. For a true azeotropiccomposition, the liquid composition and vapor phase are essentiallyequal at a given temperature and pressure range. In practical terms thismeans that the components cannot be separated during a phase change. Forthe purpose of this invention, an azeotrope is a liquid mixture thatexhibits a maximum or minimum boiling point relative to the boilingpoints of surrounding mixture compositions. An azeotrope or anazeotrope-like composition is an admixture of two or more differentcomponents which, when in liquid form under given pressure, will boil ata substantially constant temperature, which temperature may be higher orlower than the boiling temperatures of the components and which willprovide a vapor composition essentially identical to the liquidcomposition undergoing boiling. For the purpose of this invention,azeotropic compositions are defined to include azeotrope-likecompositions which means a composition that behaves like an azeotrope,i.e., has constant-boiling characteristics or a tendency not tofractionate upon boiling or evaporation. Thus, the composition of thevapor formed during boiling or evaporation is the same as orsubstantially the same as the original liquid composition. Hence, duringboiling or evaporation, the liquid composition, if it changes at all,changes only to a minimal or negligible extent. This is in contrast withnon-azeotrope-like compositions in which during boiling or evaporation,the liquid composition changes to a substantial degree. Accordingly, theessential features of an azeotrope or an azeotrope-like composition arethat at a given pressure, the boiling point of the liquid composition isfixed and that the composition of the vapor above the boilingcomposition is essentially that of the boiling liquid composition, i.e.,essentially no fractionation of the components of the liquid compositiontakes place. Both the boiling point and the weight percentages of eachcomponent of the azeotropic composition may change when the azeotrope orazeotrope-like liquid composition is subjected to boiling at differentpressures. Thus, an azeotrope or an azeotrope-like composition may bedefined in terms of the relationship that exists between its componentsor in terms of the compositional ranges of the components or in terms ofexact weight percentages of each component of the compositioncharacterized by a fixed boiling point at a specified pressure.

The present invention provides a composition which comprises effectiveamounts of hydrogen fluoride and HCFO-1233xf to form an azeotropic orazeotrope-like composition. By effective amount is meant an amount ofeach component which, when combined with the other component, results inthe formation of an azeotrope or azeotrope-like mixture. The inventivecompositions preferably are binary azeotropes which consist essentiallyof combinations of only hydrogen fluoride with HCFO-1233xf.

In one embodiment, the inventive composition contains from about 6.2mole percent to about 90.7 mole percent HF, preferably from about 53.5mole percent to about 86.7 mole percent and most preferably from about79.3 mole percent to about 85.3 mole percent based on the weight of theazeotropic or azeotrope-like composition. In another embodiment theinventive composition contains from about 60 mole percent to about 71mole percent HF, preferably from about 60.2 mole percent to about 71.7mole percent HF.

In one embodiment, the inventive composition contains from about 9.3mole percent to about 93.8 mole percent HCFO-1233xf, preferably fromabout 13.3 mole percent to about 46.5 mole percent and most preferablyfrom about 14.7 mole percent to about 20.7 mole percent based on theweight of the azeotropic or azeotrope-like composition. In anotherembodiment the inventive composition contains from about 29 mole percentto about 40 mole percent HCFO-1233xf, preferably from about 28.3 molepercent to about 39.8 mole percent based on the weight of the azeotropicor azeotrope-like composition.

The composition of the present invention preferably has a boiling pointof about from 0° C. to about 61° C. at a pressure of about 15 psia toabout 107 psia. In one embodiment it has a boiling point of about 0° C.at a pressure of about 15 psia. In another embodiment it has a boilingpoint of about 25° C. at a pressure of about 38 psia. In anotherembodiment it has a boiling point of about 61° C. at a pressure of about107 psia. An azeotropic or azeotrope-like composition having about82.5±1.2 mole percent HF and about 17.5±1.2 mole percent HCFO-1233xf wasfound at 25° C.

In another embodiment of the invention, 2-chloro-3,3,3-trifluoropropene(HCFO-1233xf) may be removed from a mixture containing2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) and an impurity which may,for example, result from manufacturing steps in the preparation of2-chloro-3,3,3-trifluoropropene (HCFO-1233xf). This is done by addinghydrogen fluoride to the mixture of the 2-chloro-3,3,3-trifluoropropene(HCFO-1233xf) and impurity. Hydrogen fluoride is added to the mixture inan amount sufficient to form an azeotropic composition of the2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) and the hydrogen fluoride,and thereafter the azeotropic composition is separated from theimpurity, for example by distillation or other art recognized separatingmeans. In one embodiment, the impurity itself does not form anazeotropic mixture with 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf),hydrogen fluoride or a mixture of 2-chloro-3,3,3-trifluoropropene(HCFO-1233xf) and hydrogen fluoride. In another embodiment, the impuritydoes form an azeotropic mixture with 2-chloro-3,3,3-trifluoropropene(HCFO-1233xf), hydrogen fluoride or a mixture of2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) and hydrogen fluoride.Typical impurities of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf)include other halocarbons which may be miscible with2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) such as1,1,1,2,3-pentachloropropane; 1,1,2,3-tetrachloropropene;2,3,3,3-tetrafluoropropene;2,3-dichloro-3,3-difluoropropene(HCFO-1232xf);1,1,1,2,2-pentafluoropropane; or 1,2-dichloro-3,3,3-trifluoropropene.

The following non-limiting examples serve to illustrate the invention.

Example 1

60 g of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) were mixed with 40g of HF to form a heterogeneous azeotrope mixture. The vapor pressure ofthe mixture at about 25° C. was about 38 psia.

Example 2

Binary compositions containing solely 2-chloro-3,3,3-trifluoropropene(HCFO-1233xf) and HF were blended to form a heterogeneous azeotropemixtures at different compositions. The vapor pressures of the mixtureswere measured at about 0, 25 and 61° C. and the following results werenoticed. Table 1 shows the vapor pressure measurements of HCFO-1233xfand HF as a function of composition with varying weight percent HF atconstant temperatures of about 0, 25, and 61° C. The data also showedthat HCFO-1233xf/HF is a heterogeneous mixture.

TABLE 1 P-T-X of HCFO-1233xf/HF Pressure (Psia) Mole % HF T = 0° C. T =25° C. T = 61° C. 0.00 8.87 22.88 64.58 12.70 14.21 35.2 85.62 22.5014.69 38.48 102.4 38.34 15.03 38.4 106.08 46.46 15.03 38.35 107.34 55.0615.03 38.45 106.95 67.39 15.03 38.45 106.95 76.06 15.03 38.45 107 81.7215.03 38.45 107.05 86.27 15.08 38.4 102.88 98.36 12.51 29.04 72.53 99.309.7 23.17 61.72 100.00 6.87 17.82 52.43

The data also shows that the mixture is azeotropic or azeotrope-likesince the vapor pressure of the mixtures of HCFO-1233xf and HF ishigher, at all indicated blend proportions, than vapor pressures ofHCFO-1233xf and HF alone, i.e. as indicated in the first and last rowsof Table 1 when HF is 0.0 mole % and HCFO-1233xf is at 100.0 mole % aswell as when HCFO-1233xf is at 0.0 mole % and HF is at 100.0 mole %. Thedata from Table 1 is shown in graphic form in FIG. 1.

Example 3

The azeotropic or azeotrope-like composition of the HCFO-1233xf/HFmixture was also verified by Vapor-Liquid-Liquid equilibrium (VLLE)experiment. 63.5 g of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) weremixed with 36.5 g of HF to form a heterogeneous mixture (visualobservation) at 24° C. The vapor composition, upper liquid (HF rich),and bottom liquid (organic) were sampled. The result shows that theazeotropic composition is about 82.5±1.2 mole percent HF at 24° C.

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily appreciatedby those of ordinary skill in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe invention. It is intended that the claims be interpreted to coverthe disclosed embodiment, those alternatives which have been discussedabove, and all equivalents thereto.

What is claimed is:
 1. An azeotropic or azeotrope-like composition whichconsists essentially of hydrogen fluoride and2-chloro-3,3,3-trifluoropropene.
 2. The azeotropic or azeotrope-likecomposition of claim 1, which consists of hydrogen fluoride and2-chloro-3,3,3-trifluoropropene.
 3. The azeotropic or azeotrope-likecomposition of claim 1 comprising, from about 12 mole percent to about98 mole percent hydrogen fluoride and from about 2 mole percent to about88 mole percent 2-chloro-3,3,3-trifluoropropene, which composition has aboiling point of from about 0° C. to about 61° C. at a pressure of fromabout 15 psia to about 107 psia.
 4. The azeotropic or azeotrope-likecomposition of claim 3, wherein the hydrogen fluoride is present in theamount from about 12 mole percent to about 86 mole percent and the2-chloro-3,3,3-trifluoropropene is present in the amount from about 14mole percent to about 88 mole percent.
 5. The azeotropic orazeotrope-like composition of claim 4, wherein the hydrogen fluoride ispresent in the amount from about 38 mole percent to about 86 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 14 mole percent to about 62 mole percent.
 6. The azeotropicor azeotrope-like composition of claim 4, having a boiling point ofabout 0° C. at a pressure of about 15 psia.
 7. The azeotropic orazeotrope-like composition of claim 3, wherein the hydrogen fluoride ispresent in the amount from about 22 mole percent to about 86 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 14 mole percent to about 78 mole percent.
 8. The azeotropicor azeotrope-like composition of claim 7, wherein the hydrogen fluorideis present in the amount from about 38 mole percent to about 86 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 14 mole percent to about 62 mole percent.
 9. The azeotropicor azeotrope-like composition of claim 7, having a boiling point ofabout 25° C. at a pressure of about 38 psia.
 10. The azeotropic orazeotrope-like composition of claim 7, wherein the hydrogen fluoride ispresent in the amount from about 38 mole percent to about 81 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 19 mole percent to about 62 mole percent.
 11. The azeotropicor azeotrope-like composition of claim 10, having a boiling point ofabout 61° C. at a pressure of about 107 psia.
 12. The azeotropic orazeotrope-like composition of claim 1 having a boiling point of fromabout 0° C. to about 61° C. at a pressure of from about 15 psia to about107 psia.
 13. The azeotropic or azeotrope-like composition of claim 1,wherein the azeotropic or azeotrope-like composition is heterogeneous.14. The azeotropic or azeotrope-like composition of claim 13 comprising,from about 12 mole percent to about 98 mole percent hydrogen fluorideand from about 2 mole percent to about 88 mole percent2-chloro-3,3,3-trifluoropropene, which composition has a boiling pointof from about 0° C. to about 61° C. at a pressure of from about 15 psiato about 107 psia.
 15. The azeotropic or azeotrope-like composition ofclaim 14, wherein the hydrogen fluoride is present in the amount fromabout 12 mole percent to about 86 mole percent and the2-chloro-3,3,3-trifluoropropene is present in the amount from about 14mole percent to about 88 mole percent.
 16. The azeotropic orazeotrope-like composition of claim 15, wherein the hydrogen fluoride ispresent in the amount from about 38 mole percent to about 86 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 14 mole percent to about 62 mole percent.
 17. The azeotropicor azeotrope-like composition of claim 15, having a boiling point ofabout 0° C. at a pressure of about 15 psia.
 18. The azeotropic orazeotrope-like composition of claim 14, wherein the hydrogen fluoride ispresent in the amount from about 22 mole percent to about 86 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 14 mole percent to about 78 mole percent.
 19. The azeotropicor azeotrope-like composition of claim 18, wherein the hydrogen fluorideis present in the amount from about 38 mole percent to about 86 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 14 mole percent to about 62 mole percent.
 20. The azeotropicor azeotrope-like composition of claim 18, having a boiling point ofabout 25° C. at a pressure of about 38 psia.
 21. The azeotropic orazeotrope-like composition of claim 18, wherein the hydrogen fluoride ispresent in the amount from about 38 mole percent to about 81 molepercent and the 2-chloro-3,3,3-trifluoropropene is present in the amountfrom about 19 mole percent to about 62 mole percent.
 22. The azeotropicor azeotrope-like composition of claim 21, having a boiling point ofabout 61° C. at a pressure of about 107 psia.